Radiation in the natural world is principally divided into a component originating from the sun, termed shortwave radiation, and a component originating from inorganic and materials on Earth, termed longwave radiation. These sources of radiation are composed of light that varies by wavelength, owing to the chemical composition of the atmosphere and materials on Earth, and the fractional contribution of radiation from these sources incident on any particular point. Radiometers are optical devices that measure radiation across a broad spectrum of wavelengths, in the shortwave or longwave region, with the intent of measuring the total energy across the spectrum in that region. Spectrometers are optical devices that receive radiation and quantify the energy of light received in comparatively narrow wavelengths to produce a spectrum. The spectrum, which also may be called a spectral density, is a distribution of intensity of the optical radiation input to the spectrometer as a function of a wavelength. A detecting element transforms the radiation, in broad or narrow spectral regions, into an electrical form after which a signal processor may be used to analyze the spectrum by, for example, quantifying the amount of each wavelength component that is present in the input optical radiation.